This invention relates to a method and means for improving mechanical ventilation for livestock confinement buildings.
A good ventilation system for livestock confinement buildings is essential for the health, well-being, and development of the confined animals. The ventilation system accomplishes the following three tasks: air exchange between the interior of the building and the exterior environment to replenish oxygen and to remove moisture, waste gases and dust, air circulation within the building to produce an evenly tempered, uniform living environment for the animals, and heating or cooling to maintain the temperature within a chosen optimum range for the animals.
Two alternative types of ventilation systems are generally used to provide ventilation for animals, either natural ventilation systems or mechanical ventilation systems.
Natural ventilation systems rely upon the wind passing through openings, such as windows or continuous openings along the sides of the building, and upon thermal currents created by the natural buoyancy of heated air within the building. Fresh air therefore enters the building and circulates through the confinement space and then exits on the down-wind side of the building and through vents in the ridge or other high point in the roof, removing moisture, waste gases, and dust with the exiting air stream. Although natural ventilation may be less costly to construct and to operate, ventilation reliability is unpredictable because its operation is greatly dependent upon the forces of nature, over which the system generally has only minimum control.
Mechanical ventilation systems use powered exhaust fans to slightly reduce the air pressure within the building and thereby causing fresh air to be drawn into the space to be ventilated while the fans discharge the moisture, gases, and dust from the building. The incoming fresh air is conveyed into the building through specific air inlet locations. The air inlet locations are chosen by one skilled in the art of ventilation according to specific engineering practice so that these locations cooperate in developing good fresh air distribution throughout the building.
The air inlet locations are generally equipped with devices called air inlets that attempt to regulate the volume flow of fresh air, its incoming speed, and its direction into the building. The air inlet regulates the volume flow of the fresh air to balance the fresh air requirement of the animals with the need to conserve or expel heat from within the building and to proportionately match the variable exhaust capacity of the exhaust fans. The air inlet controls the speed of the incoming air to regulate the distance that the air stream penetrates into the ventilated space and the circulation pattern that results within that space. The air inlet also directs the incoming air into the building. In the wintertime the goal is to maximize mixing time for the incoming cold air with the warm interior air and therefore avoid stressful drafts. In summertime the goal is to optimize the cooling effect of the incoming fresh air on the animals.
Mechanical ventilation systems use a wide variety of means and methods for air inlets including both automatic self-regulating air inlets that respond only to the slight vacuum created by the exhaust fans and also manually set and power-driven air inlets with regulation devices which sense the operation of the exhaust fans or the vacuum that they create. Automatic self-regulating air inlets are generally preferred over manually set air inlets because the latter require continuous supervision labor and are preferred over power-driven air inlets because the latter are more costly, complicated, and less reliable in operation.
Automatic self-regulating air inlets may be designed specifically for use in the ceiling, on the sidewall, or with slots in the juncture between the ceiling and sidewall of the building.
The proper operation of automatic air inlets is generally effected by wind pressure. This wind pressure, by its very nature, is variable and unpredictable. Its effect on the performance of air inlets and, by extension, the ventilation system can be seriously detrimental to achieving the goals of the ventilation system.
This invention relates to specific methods and means that define the design and construction of an improved automatic self-regulating air inlet device which minimizes the effect of wind pressure on air inlet performance and which is positioned in the ceiling joists, between the roof and the confinement space, of confinement buildings.